It is often desirable to minimize the influence of interference sources and also to estimate characteristic parameters of interference sources disturbing an electronic system, such as jammers or unintentional Radio Frequency Interference (RFI) disturbing a radar or a communications system. Today a separate Side Lobe Cancelling system (SLC) is used to minimize the interference from interference sources and a separate ESM (Electronic Support Measurement) receiver is today normally used to estimate interference parameters from the interference sources. The ESM system is also used for other purposes. An alternative is that this function of estimating interference parameters is performed by the electronic system. Both alternatives limit the time available for the actual function of the electronic system as both solutions will occupy the antenna aperture of the electronic system during operation. Antenna availability is a critical factor in Multifunctional systems where an antenna aperture can be used by several systems as e.g. a radar system, ESM system and a communication system.
SLC systems are used to cancel e.g. jammer signals picked up in side lobes of a radar stystem. Existing solutions allow jammer signals from several jammer sources to be cancelled. One solution is described in U.S. Pat. No. 4,044,359 “Multiple Intermediate frequency side-lobe canceller”. Side lobes are difficult to avoid when designing antennas and jammer signals can be picked up by these side lobes. As the jammer signals are often powerful they will cause interference with the signal from a target picked up in the main lobe even if the reception sensitivity of the side lobe is much below the reception sensitivity of the main lobe. The drawback with the existing SLC solutions of today is that only narrow band cancellation of the side lobe is possible. This is a serious problem as radar antennas are often operating over a very wide bandwidth while side lobe cancellation is only effective in a part of the operating bandwidth of the radar antenna. SLC systems can also be used in other applications as e.g. to minimise RFI interference on communication systems.
There is thus a need to accomplish an improved method and antenna system for minimizing the influence of interference sources over a wide bandwidth and optionally for estimating interference source parameters from e.g. jammers without the estimation causing interruption of neither the normal function of the electronic system nor the normal ESM function.